Percussive hand tool



APrf?, 1929- s. J. BROWN 1,'08,658

PERCUSSIVE HAND TOOL Filedl May 14, 1928 z fly-f' 22?' Z' n am @im @Mgg/Ta@ Patented Apr. 9, 1929.

` UNiTEn j sra-TES 1,708,658 PATENT OFFICE.

sumar :raMns Baown, or Lennon, ENGLAND, AssreNoR To SIDNEY JAMES BROWN l AND WILLIAM GUY-rnLL.

rnnoussrvn EAN13 TooL.

Application led May 14, 1928, `Serial No. 277,683, and in Great Britain May 14, 1927.

This invention relates to percussive drills embodying a hammer member operated by r tary means.

rl`he object of the invention is to provide an improved device of the kind referred to with various features, whichare individually advantageous, contributing collectively to Vthe production of a tool combining lightness and coinpactness with effective percussion and a reduction of the -usual recoil or vibration, as well as a tool which can be used to drill holes in corners. n

The principal feature of the invention consists in the employment of a cam in the form of a single or multiple start buttress threaded Vhelix or worm, working against a suitably shaped companion rack attached V.to the hainmer member, which cani, in addition to being 'particularly smooth in action in producing reciprocation of the lianimer'inay be conven- V iently used to produce rotation of the tool when desired. i

But in order that the invention may A.be more readily understood and easily carried into eifectit will now be further described with the aid of the accompanying drawings wherein Figs. 1 and 2 are views at right anglee to one another of a percussive hand drill for use more particularly in boring holes in walls and the-like intended to receive plugs into which screws are subsequently to be driven. i F ig. Bis a sectional view of a portion of 1 and Fig. 4 is a corresponding view with the parts in another position. Fig. is another view of one of t-lie elements of Fig. 3 and Fig. 6 is another view of one ot the elements removed from Fig. 1.

As here shown, a drill `1 is inserted in a holder 2 the stem 3 whereof is an ea sy d'within a sleeve e attached to, or forming part of, a frame 5 provided with a handle 6, pressure applied to which will be transmitted by way of the sleeve t to the holder through the shoulder of the latter. 7 is the hammer headirixec by a screw 8 to a lever 9 pivoted at 10 between Athe aws of a forked bracket 11 which may be removably secured to the frame 5 as by a set screw. This lever 9 is acted upon by a helical spring v12 encircling` a stationary post 13 which passes through an aperture 14 in the lever and is furnished with a nut 15 having a milled edge and adapted to vary the force exerted by the spring upon the lever.. For

' the purpose of retracting the lever it is provided with aY rack 16 having teeth more or less complementary to four buttress threads 17 constituting a worm adapted to be rotated by a crank handle 18 upon a spindle 19. This spindle 19 may conveniently work in bearings 20, 21, the bearing 2() being permanently attached to t-lie frame 5 and the other bearing 21 removably secured, as by a set screw 22.

rlhe raclr 16 is preferably secured to the lever 9 by a screw threaded stem 23 and nut.

F or the purpose of continuously rotating the drill, a worm wheel 24 (Figs. 1 and 6) is fixed upon the steinV 3 of the drill holder, said wheel having teeth adapted to mesh with the worm 17. The boss 25 of this wheel positions the tool holder stem 3 in the sleeve 4 with a certain amount of clearance at 26.

When .the tool is not in use the rack 16 bearsfully upon the worm 17 and the lever 9 will in consequence be inclined somewhat towards the front of the frame and not as illustrated, so that there is clearance between the tool holder 2 and the sleeve which disappears when, as assumed, pressure is applied to the handle 6 whilst using the tool. In other worde, when the tool is in use the parts occupy the position shown where the end of the stem 3 engages the screw 8 and has slightly displaced the lever 9 and hammer head 7. In this way jar between the worm and rack during operation is lessened.

F rom the foregoing it will be understood that as the crank handle 18 is turned, the worm threads 17 acting upon the rack 1G after the manner of a screw thread upon a part nut held against axial movement, will gradually displace the rack and its lever 9 from the position shown in Fig. 3 to that shown in Fig. 4 after which the raclr 16 and lever 9 are liberated and allowed to return rapidly under the action of spring' 12, thus imparting a sharp 9 blow to the stein 3 of the tool holder 2. The

use of a multiple worm thread enables a series of blows to be imparted per revolution of the cani. Thuswhereas in the case of a single helix or worin thread it is necessary, for

Ycontinuity of action, that the rack shall be Cil Cri-

hammer head 7 on the other hand moving through a much greater distance andrmore Yrapidlydue to the difference in theleverage movements. A very effective' percussive aetion thus results, and it will be found that'the recoil of the frame is materiallyreduced;

Thefact furthermore that the cama'cts upon the lever 9 at-a greater distance from Jeherpivot 10 than does the spring 12 lessens the pressure exertedbetween the cam andthe rack f VThe Whole arrangement is Vsuch that the axis of the Worm 17 can be disposed midway, or substantially midway, between the major i limbs of the-*frame 5 so thatthe cranl; handle 18vi's located approximately centrally ofthe holdinghandle G, and the axis of the tool,

holderk can be located nearer to one such limb of the frame thanto the other, thusenabling holes to be drilledV close to obstructions in different planes such as areformed by the sidewall and ceiling at the corner of a room for example. The crank handle 18 is formed with a screw. threaded hole so that it. can be f l quickly applied' to and removed from a screw threadedl hole, or holes, to enablev the lengthV of the driving arm to be varied.' KVAlso if de- A sired the spindle 19 may, as shown in Figs.

2, 3- and 4 be extended at the opposite end to enable the handle 18 toibefitted thereto when opposite'handed corners are for exf ample being dealt with, the said spindle'end l having a left hand thread and the handle 18 provided With an additional hole as at 18a also With left hand thread. i Or two separate handles may bel employed.

lf desired `the parts may be Venclosed to a being illustrated as litt-ed for that purpose.

. Itis to be understood that various modications can be effected.`

The construction of thetool is such that rei moval'of theprincipal parts can be, readily effected- .VVh'at I claim is i 1. A tool of the kind referred to, comprising aframe, a hammer head, resilient means through which the head reactsagainst the fram-e, a member embodying a. raclrtowhich the hammer head is secured, a. buttress thread-V ed Worm cooperating With ther-ack and adaptf ed to retract theV hammer head therethrough', and means for Vmanually rotating the Worm, substantially as described. Y Y 2. A tool according to :claim 1, wherein the member to which the hammer head is secured is' angula-rly movable.

3. A tool according to claim 1 wherein thel member to which thehamrner head is se# cured is a4 leverpivoted at vone end andthe resilientY means through-Which. the head reacts against the'.y frame isdisposed between the headk and the pivotal connection of the lever. I f

4. A toolV according to claim lwherein the Worm is formed by a multi-start thread.

Atool according toclaim 1 wherein a tool holder is4 employed having aivorm Wheel adapted" to be engaged and rotated by the Worm Which retracts the hammer. Y f Signed at London, England, this 21stday of April, 1928. y

, v- ASIDNEY JAMES BROVN.

7 greater or lesser extent, two coverplates 27 

